Our neighbor downstairs brought bed bugs into the building and we've been struggling to get rid of them and keep them out of our apartment, as he's not doing his part to get rid of them as well. It had gotten so bad that we were waking up from our sleep itching and in pain (I'm especially sensitive to their bites). We had tried diatomaceous earth and insecticide spray under the bed because it worked before at a different residence, but that didn't help this time. Finally, though, a combination of bedding/home spray for the mattress, the encasement, plus Ortho spray and diatomaceous earth, we've had over a week of not getting bitten at all. We're still working on treating the rest of the apartment, but this is a major win in this war!
I had researched and found that the TPU material lining the inside of the encasement prevents the bugs from escaping but doesn't suffocate them. Trapped inside for at least 12-18 months, though, they will die of starvation. Keep that in mind if considering this as an option. We plan on leaving the encasement on the bed until we buy a new mattress.
I definitely plan on getting another one of these when we do get a new mattress so we don't have to worry about it getting infested.